[charts/gateway] Update license info in Prerequisites section of README

[jennarddy]

Description of the change

Reference to Gateway version is removed in the license info. Provided GW 11 and 10 examples.

Benefits

We don't have to update the license info in future anymore since the Gateway version reference is removed.

Drawbacks

None

Applicable issues

• fixes #

Additional information

Checklist

• [X] Chart version bumped in Chart.yaml according to semver.
• [X] Variables are documented in the README.md
• [X] Title of the PR starts with chart name (e.g. [charts/gateway])
• [X] If the chart contains a values-production.yaml apart from values.yaml, ensure that you implement the changes in both files

[jennarddy]

Already addressed in stable